1. Field of the Invention
This invention relates to a process for preparing a over-based alkaline earth metal phenate sulfide or sulfurized alkaline earth metal phenate by reacting a starting mixture in which the amount of a phenol is present in excess, and is directed to the commercially advantageous production of chemicals which are useful mainly as detergents or alkaline detergents for lubricating oils or fuel oils.
2. Description of the Prior Art
Basic phenates are generally used in lubricating oils for internal combustion engines, and exhibit a marked effect in preventing corrosive wear, formation of piston ring groove deposits, piston ring sticking, etc., by neutralizing or dispersing acids such as oxy acids or sulfuric acid, sludge, lacquers, carbon, etc.
From the standpoint of the function of acid neutralization, phenates can be classified into two types, one type being called normal phenates containing a theoretical amount, one gram equivalent, of metal per phenolic hydroxyl group; and the other type being called basic phenates or over-based phenates, e.g., as disclosed in U.S. Pat. No. 3,464,970 and British Pat. No. 1,280,749, containing metal in an amount larger than the theoretical amount, wherein a theoretical amount of 100% is considered the reaction of 1 gram equivalent of alkaline earth metal reacted per phenolic hydroxyl group (hereinafter the same). The present invention relates to a novel process for preparing basic or over-based phenates containing metal in an amount larger than the theoretical amount.
Heretofore, two typical methods for introducing sulfur into a phenate have been known. One method comprises converting an alkyl phenol to the sulfide thereof using sulfur monochloride or sulfur dichloride or the like and then converting the sulfide to a metal salt. The other method comprises sulfurizing the phenol at the time of adding a metal, or sulfurizing the metal phenate, using elemental sulfur. The present invention is based on the latter method of sulfurization.
Techniques relating to the latter type of sulfurization method are described in considerable detail in, for example, H. M. Drew, Metal-Based Lubricant Compositions, Chemical Technology Review, No. 48, Noyes Data Corp., Park Ridge, New Jersey, (1975), pp. 6-15. Those considered to be comparatively relevant to the present invention are described below.
U.S. Pat. Nos. 2,680,096 and 2,680,097, for example, describe a process for preparing sulfurized phenates by heating a mixture of an alkyl phenol, an alkaline earth metal oxide or hydroxide, ethylene glycol and sulfur. This process is the first successful utilization of the finding by L. Haitinger (as disclosed in Monat Chemie, 4, 165 (1883)) on the reaction of sodium phenoxide with elemental sulfur in a method of preparing lubricating oil additives. However, these basic phenates were considered to be only half-finished products as lubricating oil additives in view of their stability or oil solubility.
The method, for example, disclosed in U.S. Pat. No. 3,036,971, is considered an advance over the process disclosed in U.S. Pat. No. 2,680,096 in the use of an additional step of treating the product obtained with carbon dioxide.
However, in these processes, a basic phenate containing a calcium content of only about 170%, based on the theoretical amount, can be obtained even if calcium hydroxide is used in an amount of slightly more than 200% of the theoretical amount based on the starting alkyl phenol (see U.S. Pat. No. 3,036,971).
The method disclosed in U.S. Pat. No. 3,194,761 is a basic improvement in the process described in U.S. Pat. No. 3,036,971 and is successful in incorporating calcium in the alkyl phenol in an amount of about 1.5 times the amount of calcium incorporated in U.S. Pat. No. 3,036,971.
British Pat. No. 900,059 discloses a process quite similar to those set forth in U.S. Pat. Nos. 2,680,096 and 3,036,971, i.e., a process comprising reacting an alkylphenol with elementary sulfur, an alkaline earth metal salt and a dihydric alcohol, removing only water from the reaction product, heating the water-free reaction product together with carbon dioxide in the presence of a dihydric alcohol, and then reacting the resultant product additionally with the dihydric alcohol and alkaline earth metal salt. In this process, the amount of alkaline earth metal reacted at one time is small.
These methods in U.S. Pat. No. 3,194,761 and British Pat. No. 900,059, however, require an additional step, in which a polyhydric alcohol and calcium hydroxide must be added again.
On the other hand, U.S. Pat. No. 3,178,368 discloses a successful incorporation of a large quantity of an alkaline earth metal based on the alkyl phenol. According to this method, an alkaline earth metal sulfonate and a small amount of a higher alcohol must be further added to the starting materials used in the process described in U.S. Pat. No. 3,036,971.
On the other hand, Sakai and the present inventor have discovered the presence of a group of over-based phenates containing a larger excess of alkaline earth metal than prepared in conventional methods, and processes for their production (e.g., as disclosed in Japanese Pat. Nos. 533,078, 533,079 and 613,542; T. Hori et al., Bull. Japan Petrol. Inst., 16, 1 (1974); ibid., 16, 106 (1974); ibid., 17, 193 (1975)). These processes essentially require the use of a higher alcohol.
The known techniques described above each have their own characteristics as set forth hereinabove. These prior techniques are based on a fundamentally important common technical concept. An especially important aspect of this common technical concept is the mixing ratio between the phenol and the alkaline earth metal agent in the preparation of basic phenates. All of the conventional techniques have employed the method typically exemplified by the statement by W. T. Stewart and F. A. Stuart in Advances in Petroleum Chemistry and Refining, J. J. Mcketta, Jr., Ed., Vol. 7, Interscience Publishing Company, New York (1963) that "Basic phenates can be produced by use of an excess of alkaline earth metal oxides or hydroxides over the theoretical amounts required to form the normal phenate, (i.e., one equivalent of metal per equivalent of substituted phenol), namely by using alkaline earth metal oxides or hydroxides in excess of the gram equivalent of the alkyl phenol." In addition, the disclosure in U.S. Pat. Nos. 2,680,096, 2,680,097, 3,036,971 and 3,178,368 and other prior art is that it is preferred to use a blending ratio between the alkaline earth metal agent and the phenol of 5 to 10% larger than the ratio between the alkaline earth metal and the phenol desired in the final basic phenates. Such a technical concept on the blending ratio between the alkaline earth metal agent and the phenol, as far as is known, apparently has been quite universal in the field of producing these basic phenates.
On the other hand, from a commercial viewpoint, the conversion yield based on the alkaline earth metal agent in these prior techniques is low, and the content of the alkaline earth metal in the final products is at most about 170% based on the theoretical amount. To increase the metal in the final products requires a repetition of a metal addition step or the use of a higher alcohol solvent. Hence, the entire process becomes complicated since the process requires a solvent recovery step, for example.